From fc04cafc39bc694473a2b8a34ea578dc6fcf4562 Mon Sep 17 00:00:00 2001
From: MikeDvorskiy <mikhail.dvorskiy@intel.com>
Date: Thu, 26 Sep 2024 11:31:10 +0200
Subject: [PATCH] [oneDPL][ranges][zip_view] + begin_imp, end_impl to reduce
 code duplication

---
 include/oneapi/dpl/pstl/zip_view_impl.h | 54 ++++++++++++-------------
 1 file changed, 26 insertions(+), 28 deletions(-)

diff --git a/include/oneapi/dpl/pstl/zip_view_impl.h b/include/oneapi/dpl/pstl/zip_view_impl.h
index 6b3afad9e01..913724ee0c8 100644
--- a/include/oneapi/dpl/pstl/zip_view_impl.h
+++ b/include/oneapi/dpl/pstl/zip_view_impl.h
@@ -293,25 +293,22 @@ class zip_view : public std::ranges::view_interface<zip_view<Views...>> {
                                                     tuple_type<std::ranges::sentinel_t<const Views>...>>;
 
         end_type end_;
-    }; // class sentinel    
+    }; // class sentinel
 
-    constexpr auto begin() requires (std::ranges::range<Views> && ...) // !simple_view?
-    {
-        auto __tr = [](auto... __args) { return iterator<false>(__args...);};
-        return apply_to_tuple(__tr, std::ranges::begin, views_);
-    }
-
-    constexpr auto begin() const requires ( std::ranges::range<const Views> && ... )
+private:
+    template<bool Const>
+    constexpr auto begin_impl()
     {
-        auto __tr = [](auto... __args) { return iterator<true>(__args...);};
+        auto __tr = [](auto... __args) { return iterator<Const>(__args...);};
         return apply_to_tuple(__tr, std::ranges::begin, views_);
     }
 
-    constexpr auto end() requires (std::ranges::range<Views> && ...) // requires !simple_view {
+    template<bool Const>
+    constexpr auto end_impl()
     {
         if constexpr (!zip_is_common<Views...>)
         {
-            auto __tr = [](auto... __args) { return sentinel<false>(__args...);};
+            auto __tr = [](auto... __args) { return sentinel<Const>(__args...);};
             return apply_to_tuple(__tr, std::ranges::end, views_);
         }
         else if constexpr ((std::ranges::random_access_range<Views> && ...))
@@ -322,29 +319,30 @@ class zip_view : public std::ranges::view_interface<zip_view<Views...>> {
         }
         else
         {
-            auto __tr = [](auto... __args) { return iterator<false>(__args...);};
+            auto __tr = [](auto... __args) { return iterator<Const>(__args...);};
             return apply_to_tuple(__tr, std::ranges::end, views_);
         }
     }
 
+public:
+    constexpr auto begin() requires (std::ranges::range<Views> && ...) // !simple_view?
+    {
+        return begin_impl<false>();
+    }
+
+    constexpr auto begin() const requires ( std::ranges::range<const Views> && ... )
+    {
+        return const_cast<zip_view*>(this)->begin_impl<true>();
+    }
+
+    constexpr auto end() requires (std::ranges::range<Views> && ...) // requires !simple_view {
+    {
+        return end_impl<false>();
+    }
+
     constexpr auto end() const requires (std::ranges::range<const Views> && ...)
     {
-        if constexpr (!zip_is_common<Views...>)
-        {
-            auto __tr = [](auto... __args) { return sentinel<true>(__args...);};
-            return apply_to_tuple(__tr, std::ranges::end, views_);
-        } 
-        else if constexpr ((std::ranges::random_access_range<Views> && ...))
-        {
-            auto it = begin();
-            it += size();
-            return it;
-        }
-        else
-        {
-            auto __tr = [](auto... __args) { return iterator<true>(__args...);};
-            return apply_to_tuple(__tr, std::ranges::end, views_);
-        }
+        return const_cast<zip_view*>(this)->end_impl<true>();
     }
 
     constexpr auto size() requires (std::ranges::sized_range<Views> && ...)